Flexible endoscopes including optical fibers are used for a variety of endoscopic procedures such as endoscopic papillotomy and the evaluation of esophageal varices, arteriovenous malformations, ulcer vessels, ischemic bowel disease, and polyps.
Endoscopic papillotomy is a nonoperative technique which enables relief of common bile duct obstruction due to retained gallstones. In this technique, a flexible endoscope is inserted into the duodenum and advanced until the entrance to the common bile duct and the pancreatic duct (i.e., the papilla of Vater) can be visualized. A papillotome catheter is then passed through the biopsy channel of the endoscope until the catheter tip exits from the endoscope tip, and the endoscope tip is remotely manipulated and the papillotome catheter is concurrently advanced so as to insert the papillotome catheter into the common bile duct. Along its side adjacent its tip, the papillotome catheter carries an elongated wire that can be remotely bowed so as to bear upon the roof of the papilla. By passing an electrosurgical current through the wire when the papillotome catheter has been appropriately positioned and bowed, the roof of the papilla of Vater may be cut so as to enlarge the papilla orifice. After withdrawal of the papillotome catheter, the retained gallstones in the common bile duct may naturally migrate into the duodenum or may be removed by a grasping device passed through the biopsy channel of the endoscope.
In certain patients, the retroduodenal artery is quite close to the papilla and may be cut by the papillotome catheter, thereby leading to morbidity and mortality complications. To reduce the risk of endoscopic papillotomy, it is highly desirable to determine the location of the retroduodenal artery relative to the papilla of Vater by detecting the presence and characteristics of blood flow in the retroduodenal artery.
Esophageal varices are dilated veins on the inner surface of the esophagus, most typically resulting from cirrhosis of the liver, and quite often bleed. Although pharmaceutical and surgical methods typically are used to treat esophageal varices, an endoscopic technique also may be used in which a flexible endoscope is inserted into the esophagus and advanced until a varix is visualized. A catheter having a hollow needle at its tip is then passed through the biopsy channel of the endoscope so that the needle exits from the endoscope tip, and the endoscope tip is remotely manipulated and the catheter is concurrently advanced until the needle is inserted into the varix. A sclerosing agent is then injected through the catheter and the needle into the varix in order to thrombose or clot the varix.
Occasionally, a heavy esophageal mucosal fold may mimic the appearance of a varix. It is therefore highly desirable to determine if the visualized target is a varix by the detection of venous flow before needle insertion and sclerosing agent injection. It is also highly desirable to determine the effect of the injected sclerosing agent in the event the target is a varix by the detection of a reduction in and eventual absence of venous flow.
Another type of lesion which causes problematic gastrointestinal bleeding is that of an arteriovenous malformation which can be visualized through the use of a flexible endoscope as a small red dot on the mucosa of the gut. Unfortunately, it is often very difficult to tell if such a red spot is an adherent clot, a petechiae or an arteriovenous malformation. It is therefore highly desirable to positively determine such a red spot as an asteriovenous malformation by the detection of arterial blood flow.
In a similar manner, the evaluation of ulcerations in the stomach or duodenum and of techniques being used to thrombose such ulcerations, the diagnosis of ischemic bowel disease, and the evaluation of the size of the blood vessels in the stalks of gastrointestinal polyps by use of a flexible endoscope would be facilitated by detecting the presence and characteristics of proximate blood flow.
Rigid endoscopes are used for a variety of endoscopic procedures such as peritoneoscopy, arthroscopy, proctoscopy, thoracoscopy and cystoscopy. As with flexible endoscopic procedures, rigid endoscopic procedures would benefit immensely from the detection of the presence and characteristics of proximate blood flow. For example, in the examination of an organ such as the liver in peritoneoscopy, a mass may be encountered. If the mass is an arteriovenous malformation, biopsy of the mass may result in severe life-threatening hemorrhage which could be prevented by the prior determination of the mass as an arteriovenous malformation through the detection of arterial blood flow therein.
In addition to the endoscopic procedures discussed, many surgical procedures would benefit from the detection of proximate blood flow. As examples, the detection of arterial blood flow proximate the site of an abdominal aneurysm repair or a coronary artery bypass would allow assessment of the success of the surgical procedure. Just as it is often difficult for the endoscopist to determine if a biological structure is vascular, the same problem may occur for the surgeon, and it may be very important to determine if a biological structure about to be biopsied or removed is highly vascular.
Besides detecting blood flow during endoscopic and surgical procedures, the long-term monitoring of blood flow and differentiation of arterial from venous flow in biological structures is highly desirable. For example, long-term monitoring of blood flow in an artery would permit simultaneous monitoring of heart rate and of an indication of impending shock or a change in cardiac output.
In the prior art, detection of blood flow in biological structures is accomplished by evaluation of a Doppler signal obtained from an ultrasonic transducer that ensonifies the biological structure. As of the present, no practical methods or apparatus providing a Doppler signal have been devised which can be successfully used with the endoscopic, surgical and monitoring diagnostic and therapeutic methods discussed above. In order to meet the requirements of such methods, the ultrasonic apparatus must be small in diameter and flexible so as to be capable of being passed through the biopsy channel of an endoscope or otherwise inserted into the body, must be nontoxic and must be resistant to bodily fluids when left within the body, must be capable of detecting blood flow in the biological structure of interest and of distinguishing the detected blood flow from that in adjacent biological structures, and must be capable of detecting the characteristics of blood flow so as to distinguish between arterial and venous flow.